Electrical power storage devices

ABSTRACT

An electrical storage device includes high surface area fibers (e.g., shaped fibers and/or microfibers) coated with carbon (graphite, expanded graphite, activated carbon, carbon black, carbon nanofibers, CNT, or graphite coated CNT), electrolyte, and/or electrode active material (e.g., lead oxide) in electrodes. The electrodes are used to form electrical storage devices such as electrochemical batteries, electrochemical double layer capacitors, and asymmetrical capacitors.

PRIORITY

This application claims priority to U.S. Provisional Application61/115,815 filed Nov. 18, 2008, U.S. Provisional Application 61/150,987filed Feb. 9, 2009, and International Patent Application No.PCT/US09/064992 filed Nov. 18, 2009, each of which are incorporatedherein by reference in their entirety.

BACKGROUND

1. Field of the Invention

This invention relates to the use of fibers (e.g., wicking fibers) inelectrochemical batteries, electrochemical double layer capacitors, andasymmetrical capacitors.

2. Related Art

It is known to provide electrical power storage devices, such aselectrochemical batteries and capacitors, for use in vehicles such asautomobiles. For example, lead-acid batteries have been used instarting, lighting, and ignition (“SLI”) applications.

Two of the most common electrical power storage devices are batteriesand capacitors. Conventional lead-acid batteries electrodes are formedby creating a lead paste that is applied to a substrate (e.g., a grid,plate, or screen) that may also ad, as a charge collector. As the leadpaste dries, open pores are formed within the lead paste where batteryelectrolyte may enter increasing the reactive area of the grid andincreasing its charge capacity. However, excessive porosity reduces theelectrode's structural integrity. In addition, because conventionalelectrodes have limited porosity, a significant amount of activematerial is inaccessible to the electrolyte and is underutilized oressentially wasted because it is not available for reaction. Typically,about half of the lead in conventional lead-acid electrodes is unusableor goes unused. Over its life, a battery may be charged and dischargedmultiple times, which can also degrade the electrode as thereduction-oxidation reactions that supply current are repeatedlyreversed. Over time, sections of the electrode can become electricallydisconnected from the rest of the electrode. The electrode's structuralintegrity also deteriorates over time. To hold the electrode material inplace, a scrim layer (e.g., a fiber mesh) may be used. The scrim layermat may be placed on the charge collector prior to applying the activematerial paste and/or placed over the paste after it is applied. Thescrim layer may help hold the electrode together, but it does notimprove porosity or increase reactivity.

Capacitors store power in the form of an electric field between twoconductors. Typical capacitors use stacks of thin plates (alternatingcapacitor plates and dielectric) or rolls of thin sheets (alternatingcapacitor and dielectric sheets rolled together). Energy is commonlystored on adjacent plates or sheets, separated by dielectric material,in the form of electrical charges of equal magnitude and oppositepolarity. In typical capacitors, current flows from the capacitorsurface throughout the entire capacitor plate, requiring the plates tobe conductive to reduce resistance loss and to be sufficiently thick tonot overheat and melt. Such requirements impose undesirable limits onthe capacitor's power storage to weight ratio. Capacitance (i.e., theamount of charge stored on each plate) is proportional to plate surfacearea and inversely proportional to the distance between plates. Thus,increasing a capacitor's ability to store energy often requiresincreasing plate size and/or decreasing the distance between the plates.However, increasing the plate size increases resistance and overheatingproblems and decreasing plate separation increases the risk of chargepassing directly between the plates (i.e., a short circuit), burningthem out and rendering the capacitor incapable of holding a charge.

Electrochemical double layer capacitors (“EDLC”) are power storagedevices capable of storing more energy per unit weight and unit volumethan traditional electrostatic capacitors. Moreover, FDIC can typicallydeliver stored energy at a higher power rating than conventionalrechargeable batteries. Conventional EDLC use carbon as the activematerial in the electrodes. Conventional EDLC consist of two porouselectrodes that are isolated from electrical contact by a porousseparator. Both the separator and electrodes are infused with anelectrolytic solution. This allows ionic current to flow between theelectrodes through the separator, but prevents electrical current fromshorting the cell. A current collecting grid is coupled to the back ofeach of the electrodes. EDLC store electrostatic energy in a polarizedliquid layer that forms when a potential exists between two electrodesimmersed in an electrolyte. When electrical potential is applied acrossthe electrodes, a double layer of positive and negative charges isformed at the electrode-electrolyte interface by polarization of theelectrolyte ions due to charge separation under the applied electricfield, and also due to the dipole orientation and alignment ofelectrolyte molecules over the entire surface of the electrodes. Noreduction-oxidation reactions are involved in the charge storagemechanism.

Asymmetric electrochemical capacitors use a battery electrode for one ofthe electrodes. The battery electrode has a large capacity in comparisonto the carbon electrode, so that its voltage does not changesignificantly with charge. This allows a higher overall cell voltage.Examples of asymmetrical capacitors materials include PbO₂ with carbonand NiOOH with carbon.

OUTLINE OF BASIC AND OTHER ADVANTAGEOUS FEATURES

There remains a significant need for electrical power storage devicesthat have greater power storage capacity, reduced weight, and/orimproved cyclability. It would be desirable to provide a power storagedevice, such as, for example, a battery, a capacitor, an asymmetricalcapacitor, or the like of a type disclosed in the present applicationthat includes any one or more of these or other advantageous features:

-   -   1. An electrode for a power storage device with increased        permeability without reduced structural integrity;    -   2. An electrode for a power storage device with increased        structural integrity without reducing permeability;    -   3. A power storage device that uses less active material without        reduced power capacity;    -   4. A power storage device that includes electrodes that store        energy as both an electrochemical battery and a capacitor;    -   5. A power storage device with a higher power to size ratio than        conventional power storage devices;

SUMMARY

An exemplary embodiment relates to a power storage device comprising atleast one positive electrode, at least one negative electrode, and atleast one separator separating a positive electrode from a negativeelectrode, wherein the at least one of the at least one negativeelectrode or at least one positive electrode includes high surface areafibers.

Another exemplary embodiment relates to an electrode comprising a chargecollector grid, electrode active material coated on the charge collectorgrid, and high surface area fibers.

Another exemplary embodiment relates to an electrode comprising a chargecollector comprising a mat of high surface area fibers and electrodeactive material coated on the mat.

These and other features and advantages of various embodiments ofsystems and methods according to this invention are described in, or areapparent from, the following detailed description of various exemplaryembodiments of various devices, structures, and/or methods according tothis invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the systems and methods according tothe present disclosure will be described in detail, with reference tothe following figures, wherein:

FIG. 1 is a perspective view of a vehicle including a battery moduleaccording to an exemplary embodiment;

FIG. 2 is a cut-away exploded view of a battery module according to anexemplary embodiment;

FIG. 3 is a cross-sectional view of an exemplary embodiment of atrilobal fiber according to this invention;

FIG. 4 is a cross-sectional view of a quadrilobal fiber according to anexemplary embodiment;

FIG. 5 is a cross-sectional view of a circular fiber according to anexemplary embodiment;

FIG. 6 is a cross-sectional view of a trilobal fiber loaded with carbonand coated with battery electrode active material according to anexemplary embodiment;

FIG. 7 is a partial perspective view of an electrode with a mat ofwicking fibers according to a first exemplary embodiment;

FIG. 8 is a cross-sectional view of a trilobal fiber loaded with carbonand electrolyte and coated in battery electrode active materialaccording to a second exemplary embodiment;

FIG. 9 is a cross-sectional view of a fiber with electrode activematerial coated on the interior of the fiber and permeated withelectrolyte according to an exemplary embodiment;

FIG. 10 is a front view of a dual electrochemical battery and EDLC usingfibers according to the embodiment of FIG. 9 according to an exemplaryembodiment;

FIG. 11A is a front view of a battery grid according to an exemplaryembodiment;

FIG. 11B is a front view of the battery grid of FIG. 11A covered by highsurface area fibers according to an exemplary embodiment;

FIG. 11C is a front view of the battery grid of FIG. 11B covered byelectrode active material according to an exemplary embodiment;

FIG. 12A is a cross-sectional view of a shaped fiber coated withelectrode active material according to an exemplary embodiment;

FIG. 12B is a cross-sectional view of the fiber of FIG. 12A coated witha permeable insulator according to an exemplary embodiment;

FIG. 12C is a perspective view of a mat made of the fibers of FIG. 12Baccording to an exemplary embodiment;

FIG. 13 is an end view of bicomponent filament according to a firstexemplary embodiment;

FIG. 14 is a perspective view of a bicomponent filament according to asecond exemplary embodiment;

FIG. 15 is a perspective view of a bicomponent filament according to athird exemplary embodiment;

FIG. 16 is a side view of a bicomponent filament according to a fourthexemplary embodiment; and

FIG. 17 is a side view of a bicomponent filament according to a fifthexemplary embodiment.

It should be understood that the drawings are not necessarily to scale.In certain instances, details that are not necessary to theunderstanding of the invention or render other details difficult toperceive may have been omitted. It should be understood, of course, thatthe invention is not necessarily limited to the particular embodimentsillustrated herein.

DETAILED DESCRIPTION

Referring to FIG. 1, a vehicle 160 is shown that includes an electricalpower storage device 100 according to an exemplary embodiment. Whilevehicle 160 is shown as an automobile, according to various alternativeembodiments, the vehicle may include any variety of types of vehiclesincluding, among others, motorcycles, buses, recreational vehicles,boats, and the like. According to an exemplary embodiment, vehicle 160uses an internal combustion engine (not shown) for locomotive purposes.

Electrical power storage device 100 shown in FIG. 1 is configured toprovide at least a portion of the power required to start or operatevehicle 160 and/or various vehicle systems (e.g., starting, lighting,and ignition systems (“SLI”)). Further, it should be understood thatelectrical power storage device 100 may be utilized in a variety ofapplications not involving a vehicle, and all such applications areintended to be within the scope of the present disclosure.

Electrical power storage device 100, according to an exemplaryembodiment, is illustrated in FIG. 2. In various embodiments, electricalpower storage device 100 includes several cell elements which areprovided in separate compartments of a container or housing 110containing electrolyte. The embodiment of FIG. 2 relates to automotiveapplications, wherein groups of 12-16 plates 104 and 105 are used ineach of six stacks 107 for producing a standard automotive 12-voltbattery. It will be apparent to those skilled in the art, after readingthis specification, that the size and number of the individual plates104 and 105, the size and number of plates 104 and 105 in any particularstack 107, and the number of stacks 107 used to construct electricalpower storage device 100 may vary widely depending upon the desired enduse.

In various embodiments, housing 110 includes a box-like base orcontainer and is made at least in part of a moldable resin. A pluralityof stacks 107 or plate blocks are connected in series according to thecapacity of the electrical power storage device and are accommodated inthe container or housing 110 together with the electrolyte, which iscommonly aqueous sulfuric acid.

In various embodiments, electrical power storage device 100 includes acompartment having a front wall, end walls, a rear wall, and a bottomwall. In various embodiments, five cell partitions or dividers areprovided between the end walls, resulting in the formation of sixcompartments, as typically would be present in a twelve-volt automotivebattery. In other embodiments, the number of partitions and compartmentsmay be varied to create electrical power storage devices with differentvoltages. In various embodiments, a plate block or stack 107 is locatedin each compartment, each plate block or stack 107 including one or morepositive plates 104 and negative plates 105, each having at least onelug 103, and a separator 106 placed or provided between each positiveplate 104 and negative plate 105. In various exemplary embodiments, thepositive plates 104 and negative plates 105 include a grid 101 and 102with an attached lug 103 that are coated with positive or negativeelectrode active material or paste, respectively.

Cover 111 is provided for housing 110, and in various embodiments, cover111 includes terminal bushings and fill tubes to allow electrolyte to beadded to the cells and to permit servicing. To prevent undesirablespillage of electrolyte from the fill tubes, and to permit exhausting ofgases generated during the electrochemical reaction, the electricalpower storage device may also include one or more filler hole capsand/or vent cap assemblies.

At least one positive terminal post 108 and negative terminal post 109may be found on or about the top or front compartments of the electricalpower storage device. Such terminal posts 108 and 109 typically includeportions which may extend through cover 111 and/or the front of housing110, depending upon the electrical power storage device design. Invarious embodiments, terminal posts 108 and 109 also extend through aterminal post seal assembly (not shown) to help prevent leakage of acid.It will be recognized that a variety of terminal arrangements arepossible, including top, side, or corner configurations known in theart.

FIG. 2 also shows a conventional cast-on strap 112 which includes arectangular, elongated body portion of a length sufficient toelectrically couple each lug in a plate set and an upwardly extendingmember having a rounded top. FIG. 2 also illustrates a cast-on strapcoupling lugs to be coupled to negative terminal post. As shown in FIG.2, according to various embodiments, the cast-on strap includes a bodyportion coupling the respective lugs in the end compartments and a postformed therewith to protrude through a cover.

Each cell element or chapter includes at least one positive plate 104,at least one negative plate 105, and a separator 106 positioned betweeneach positive plate 104 and negative plate 105. Separators 106 areprovided between the plates to prevent shorting and undesirable electronflow produced during the reaction occurring in electrical power storagedevice 100.

As discussed above, the reactivity of a conventional battery plate orelectrode increases as the porosity (related to the amount of voidspace) of the plate or electrode increases. However, a conventionalelectrode's structural integrity or strength and internal conductivitydecrease as porosity increases. In audition, a conventional electrode'sstructural strength and internal conductivity tend to deteriorate overtime as the battery is discharged and recharged.

The plates or electrodes described herein have greater porosity and/orstructural integrity than conventional electrodes. In various exemplaryembodiments, small high surface area fibers (e.g., shaped fibers and/ormicrofibers) with the ability to wick electrolyte solutions areincorporated into or otherwise utilized in connection with variouscomponents or parts of the electrodes. The high surface area fibers maystrengthen the electrode and/or create paths for the electrolyte tobetter penetrate the electrode active material. The resulting electrodesrequire less active material to produce the same current and retaintheir charge capacity through more discharge-recharge cycles thanconventional electrodes. They also better maintain their structuralintegrity and/or internal conductivity. In various exemplaryembodiments, non-wicking conductive fibers may also be used tostrengthen the electrode active material and increase internal electrodeconductivity.

In various exemplary embodiments, the disclosed electrodes are alsousable in electrochemical double layer capacitors (“EDLC”). Capacitanceis enhanced by the inclusion of carbon in various forms, including, forexample, graphite, expanded graphite, activated carbon, carbon black,carbon nanofibers, and carbon nanotubes (“CNT”) or any combination ofthese materials. The carbon may be provided (e.g., coated orimpregnated) in the wicking fibers and/or mixed with the activematerial. The addition of carbon to the fibers helps increase theireffective surface area and their conductivity. Conductive fibers helpprevent portions of the electrode from becoming electrically isolated(e.g., by physical and/or conductive disconnection of portions of theelectrode and/or by formation of poor conductors in the electrode). Itshould be understood that the term “electrode” as used herein refers toa device used to store electrical charge in an electrochemical batterycell, an EDLC, and/or an asymmetrical capacitor (e.g., a dualbattery/EDLC).

In various exemplary embodiments, the disclosed power storage devicescomprise asymmetrical capacitors. An asymmetrical capacitor is anelectrochemical capacitor where one of the plates is substituted with abattery electrode. In various exemplary embodiments, electrodes in thedisclosed power storage devices store electrical charge simultaneouslyas both an electrochemical battery electrode and an electrochemicalcapacitor electrode.

By way of example, FIGS. 3-5 illustrate three shaped fibers within thescope of this invention. FIG. 3 illustrates one exemplary embodiment ofa trilobal fiber 241. FIG. 4 illustrates one exemplary embodiment of aquadrilobal fiber 242. FIG. 5 illustrates one exemplary embodiment of acircular fiber 243. These and other shapes have the ability to retainmaterial coated therein without the use of or need for adhesives. Otherfiber shapes now known or later developed may also be used.

In various exemplary embodiments, the fibers have a cross-sectionaldiameter from about 1 micron to about 100 microns and 0.02-20 mm inlengths, depending on the processing method. The manufacture of wickingfibers with high surface area to volume ratios is known. For example,Largman et al. (U.S. Pat. No. 5,057,368) addresses the manufacture oftrilobal and quadrilobal fibers, the entire disclosure of which isincorporated herein by reference.

Individual fibers may be straight or non-straight. Non-straight fibersmay have one or more shapes including, but not limited to, for example,a coiled fiber, looped fiber, a crimped fiber, and an air entangledfiber. These are offered by way of example, and individual fibers mayhave sections with one or more of these or other forms.

In various exemplary embodiments, the fibers are formed from a polymer(e.g., polyester, polypropylene, polyethylene, and/or polyethyleneterephthalate). Additional materials (e.g., carbons, metals, and metaloxides) may be utilized with the polymer prior to or after fiberformation. The fibers may be formed of various organic and/or inorganicmaterials, including, for example, polypropylene, polyethylene,polyethylene terephthalate (PET), and/or glass. The fibers may also bemade of conductive polymers (e.g., redox polymers) which can act as atype I, II, or III capacitor depending on their configuration. Thechoice of materials may be affected by the environment in which theywill be placed or utilized (e.g., materials that resist the corrosiveeffects of the acids used in a cell). The fibers may be formed in asingle step or multiple steps to provide different layers of materialswith varying mechanical, chemical, electrical characteristics, and/or“fluid” transport properties. The wicking behavior of the fiber may beadjusted or altered by the choice of a hydrophobic or hydrophilic fibermaterial.

In various exemplary embodiments, the fibers may be used “as is,”carbonized, and/or pre-loaded with engineered materials (e.g., metals,carbon black, silica, tin oxide, graphite, and/or acid). In variousexemplary embodiments, the fibers are pre-treated utilizing variousmethods and/or means. The pre-loaded materials may include nano-scalematerials such as, for example, nano-fibers and multi-walled nanotubes.A coating may be applied by any suitable means, such as, for example,deposition via a solvent both in dispersion and slurry form (e.g., bywater, acid, or other solvent), by spraying, or by immersing the fiber(e.g., in a conductive metal). For example, many of the materials fromwhich the fibers may be formed have a higher melting point thanlead-based electrode active materials. Thus, lead-based active materialmay be applied to the fibers by dipping the fibers in molten activematerial and allowing the active material to stiffen, solidify, and/orotherwise form on the fiber.

In various exemplary embodiments, an EDLC is integrated with anelectrochemical battery (e.g., lead-acid or lithium ion batteries). Invarious embodiments, the battery electrodes also function as EDLCelectrodes. The electrodes may include both battery electrode activematerial and carbon. In various embodiments, the electrolyte containssufficient ions to react chemically with the battery active material andto form EDLC charged layers.

The fibers may be constructed of various materials, including conductivematerials and/or dielectric materials. In various embodiments, fibersare made from two or more materials (e.g., a conductive core and adielectric surface). The fibers may be conductive in their core orinternally (e.g., in their interiors) and dielectric on their surface orexternally, which would allow the cores to be or act as currentcollectors for the capacitors formed by the dielectric material. Thismay be accomplished at least in part by, for example, coextruding thefibers or by coating a conductive fiber with dielectric.

In various exemplary embodiments, as shown in FIG. 6, an exemplarytrilobal fiber 341 that is coated or loaded with carbon additive 246(e.g., graphite, expanded graphite, activated carbon, carbon black,carbon nanofibers, and/or CNT). Carbon materials may be loaded into oronto areas of the fiber in their native form (i.e., without any bindermaterials) or in a composite form where a known quantity of binder isadded to the carbon to form a stable porous composite (e.g., within thefiber). CNTs, carbon nanofibers, and carbon whiskers may be grown on avariety of substrates. One method of accomplishing this is disclosed inInternational Patent Application No. PCT/US2007/011577, which isincorporated herein by reference in its entirety.

In various exemplary embodiments, as shown in FIG. 6, fiber 341 (e.g.,interior surfaces) is coated with carbon and surrounded by electrodeactive material (e.g., coated on the fiber or mixed with the fibers).

In various exemplary embodiments, as shown by FIG. 7, the wicking fibersare provided or otherwise formed into a mat 222 (e.g., woven, non-woven,or point bonded). In various embodiments, active material 223 (e.g.,lead oxide) is provided (e.g., coated) on the mat 222 to form anelectrode 220 for an electrical power storage device (e.g., anelectrochemical battery). In various embodiments, as shown in FIG. 6,the fibers may also be coated with carbon (e.g., graphite, expandedgraphite, activated carbon, carbon black, carbon nanofibers, and/or CNT)and, in some embodiments, function as an EDLC. Such embodiments may helpto increase life cycle, create a high interfacial area therebyincreasing the double layer capacitance for the active electrode, helpoptimize charge acceptance and/or high-rate discharge, and/or improveconversion efficiency of active material (e.g., on initial charge).

In various alternative embodiments, short pieces of fibers areinterspersed, mixed, or otherwise provided with the active material, inaddition to or in place of the longer fibers shown in FIG. 7. Themixture of short fiber pieces and active material may be provided (e.g.,coated) on a conventional charge collector (e.g., a grid, plate, orscreen) or on a fiber mat. In various exemplary embodiments, shortlengths of fiber may be adhered to the surface of the charge collectorto help form a flocking structure to support the active material. Theinclusion of the short fiber pieces in the active material helpsincrease the electrode's porosity and/or reactivity, which helps reducethe amount of active material required to form an electrode. If thefiber pieces are coated in carbon, the resulting plate may also functionas an EDLC.

In various exemplary embodiments, a scrim layer (not shown) including afiber mesh is included in an electrode. A scrim layer may be includedbetween the active material and the charge collector and/or over orembedded at least partially in the active material. In variousembodiments, the scrim layer is formed of wicking fibers of the typesdiscussed above. The fibers comprising the scrim layer may be pre-loadedwith materials, such as, for example, electrode active material, carbon(e.g., graphite, expanded graphite, activated carbon, carbon black,carbon nanofibers, and/or CNT), silica, and/or acid. In variousexemplary embodiments, the scrim layer is formed from and/or coated orimpregnated with carbon to help improve capacitance and conductivity(e.g., in sponge lead and carbon capacitor electrodes). In otherembodiments, the scrim layer is coated or impregnated with carbon andlead oxide to form a dual electrochemical battery electrode and EDLC.The scrim layer may be formed of a woven or non-woven mesh in a varietyof patterns to adjust the ability of the scrim to adhere to and/orsupport the active material. In various exemplary embodiments, a scrimlayer may be utilized as or as part of the collector grid with thefibers coupled or connected directly to or otherwise forming or helpingform the plate connector.

FIG. 8 illustrates a cross-section of an exemplary fiber 241 at leastpartially provided (e.g., coated) with carbon 245 (e.g., graphite,expanded graphite, activated carbon, carbon black, carbon nanofibers, orCNT) and electrolyte 224 on at least some of its surfaces (e.g.,interior surfaces). In various embodiments, the fibers 241 are alsoimpregnated with electrolyte and at least partially surrounded byelectrode active material 223. In various embodiments, the averagedistance between shaped fibers 241 is approximately half the thicknessof the battery electrode. However, other spacing may be utilized.

According to various exemplary embodiments, a battery cell includes anelectrode with wicking fibers (e.g., high surface area fibers) extendinginto and/or through the electrode. In various exemplary embodiments, thewicking fibers help draw the electrolyte into the electrode (e.g., tothe electrode's interior) to help improve porosity, increasing theelectrode's effective surface area. In various exemplary embodiments,the fibers also help maintain the electrode's structural integrity byfunctioning as pasting or reinforcing fibers (e.g., against structuraldegradation caused by battery cycling).

According to various exemplary embodiments, a battery cell 230 includesan array 225 of wicking fibers (a cross-section of one exemplary fibersis shown in FIG. 9) loaded with electrode active material (e.g., alead-based paste), in various embodiments, the fiber array 225 issubstantially immersed in the electrolyte 224 solution. The fiber arrays225 may be in any form (e.g., loose fibers, woven or non-woven mats,bundles, etc.). In various embodiments, such as shown in FIG. 10, thefiber arrays 225 may act as current collectors for the electrodes, withsome loaded with anode active material and others with cathode activematerial. In various exemplary embodiments, electrodes made with suchfibers may help reduce the amount of lead required, shorten or eliminatethe drying process, do not require adhesives, and/or increaseconductivity.

According to various exemplary embodiments, carbon (e.g., graphite,expanded graphite, activated carbon, carbon black, carbon nanofibers,and/or CNT) may be added to the fibers in any of the various embodimentsshown to obtain EDLC effect from the fiber. The carbon additive helpscreate a carbon-electrolyte interface for an EDLC. In various exemplaryembodiments, the addition of CNT to the fibers also increases electricalconductivity along the fibers. In various exemplary embodiments, thefibers contain carbon and are part of an electrochemical batteryelectrode to form an asymmetrical capacitor.

According to various exemplary embodiments, the construction of anelectrode is illustrated in FIGS. 11A-11C. In various embodiments,wicking fibers are provided (e.g., loaded) with electrode activematerial. A carbon additive may also be loaded on the fibers. The fibersmay also be at least partially sheathed with battery separator. Invarious exemplary embodiments, shown in FIG. 11A, a charge collector 201(e.g., a grid, plate, or screen) is provided. The charge collector is atleast partially provided or coated with electrode fibers 222, as furtherillustrated in FIG. 11B. The fibers may be provided on one or both sidesof the charge collector and/or coupled to a terminal. In variousembodiments, as shown in FIG. 11C, the fibers 222 are at least partiallyprovided with electrode active material 223 on their exterior surfaces(e.g., exterior electrode active material may be opposite in polarity tothat loaded in the fibers' interior), which is in contact with thecharge collector. The charge collector shown is a positive collector inthe form of a lead grid or screen, but it could be any charge collectoror substrate. In some embodiments, the charge collector is a mat made atleast in part of conductive wicking fibers. Any appropriate or suitableseparator material potentially may be used, in various exemplaryembodiments, the active material provided on the interior of the fibersis not the same as that coated on the outside cathode versus anodeactive material).

In various alternative embodiments, short fiber pieces may be providedon one or more battery grids in addition to or in place of the longfibers shown in FIGS. 11B and 11C. In various embodiments, the fibersare provided or applied in a “floating structure” that may be utilizedto help support the active material.

According to various exemplary embodiments, as illustrated in FIG. 12A,a battery cell includes wicking fibers 241 coated with anode or cathodeactive material 223. As shown in FIG. 12B, the fibers 241 are at leastpartially insulated with a sheath or jacket 206 of battery separator. Invarious exemplary embodiments, as shown in FIG. 12C, the fibers 241 areformed into a mat 222 (e.g., woven or non-woven) including anapproximately equal or similar amount of anode and cathode. In otherexemplary embodiments, battery cells may be formed with separateanode-only mats and cathode-only mats.

According to some exemplary embodiments, the electrode active materialpaste is provided (e.g., mixed) with carbon such as, for example,graphite, expanded graphite, activated carbon, carbon black, carbonnanofibers, CNT, or graphite coated CNT, to help create a matrix ofcarbon within the electrode. Carbon fibers may be provided to, forexample, increase the structural strength of the electrode activematerial, the electrode's porosity, and/or the electrode's ability tofunction as an EDLC. According to various exemplary embodiments, anelectrode is manufactured by producing a master-batch of carbonnanofibers or CNT (single or multi-walled) and water (e.g., anultrasonic dispersion) or lead power (e.g., dispersed by extruder), andproviding (e.g., mixing or blending) the master-batch with electrodeactive material to form an electrode active material mixture paste. Invarious embodiments, the paste is applied or otherwise provided onto atleast a portion of an electrode substrate and dried and/or allowed todry to form an electrode plate. This may be accomplished by a variety ofmethods including, for example, rolling the mixture onto the substrate.In various exemplary embodiments, the carbon is substantially uniformlydispersed throughout the electrode. The carbon fibers may be of variousdimensions and used in various concentrations (e.g., about 0.05 to 5% ofthe electrode mixture by weight). In various exemplary embodiments, theaddition of carbon fibers increases capacitance as an EDLC withoutreducing its electrochemical battery capacity. In various exemplaryembodiments, the carbon fibers also improve the structural integrity ofthe electrode.

In various embodiments, the fibers may be made of conducting orconductive polymers which can undergo electrochemical doping (e.g.,P-doping or N-doping), thereby functioning as an electrolytic capacitor.In various embodiments, both types of electrodes (e.g., anodes andcathodes) maybe constructed of the same material capable of undergoingeither P-doping or N-doping (e.g., type III) to thereby function as anelectrolytic capacitor. In various embodiments, a scrim mat, formed atleast in part from fibers made of conducting polymers, may be added tothe electrode to provide a EMIR functionality.

In various exemplary embodiments, a power storage device is formed usingmicrofibers. For purposes of this disclosure, a “microfiber” is anyfiber with a denier per filament (“dpf”) of about 1.5 or less. Fibers ofthis kind are also sometimes referred to as “microdenier”. Themicrofibers may have any cross-sectional shape, including round.Microfibers may be used in any of the embodiments described above inaddition to or in place of the shaped fibers. Microfibers areparticularly effective at wicking liquids because of their large surfaceareas relative to their volume. Microfibers may be made of a polymer(e.g., polyester, polypropylene, polyethylene, and/or polyethyleneterephthalate).

The use of microfibers in textiles is known. For example, exemplarymicrofibers are disclosed in U.S. Pat. Nos. 6,627,025, 7,160,612, and7,431,869 and in John F. Hagewood, Ultra Microfibers: Beyond Evolution,http://www.hillsinc.net/Ultrabeyond.shtml, all of which are incorporatedherein by reference in their entirety. Microfibers of these types may beused in the disclosed power storage devices whether or not formed into afabric or mat.

In some exemplary embodiments, microfibers are formed by spinning andprocessing bicomponent filaments in the range of 2-4 dpf, after whichthe filaments are split into microfibers with a dpf of 0.1 or lower.FIG. 13 shows a bicomponent filament with a dpf of approximately 3.There are 64 microfibers of a first component in a matrix of a secondcomponent. In this embodiment, the bicomponent filament is approximately80% microfiber and 20% matrix. Because the bicomponent filament's dpf is3, the spinning may be the same as for a standard homopolymer fiber. Themicrofibers are separated from the matrix component by dissolving outthe matrix component, which process may be performed either before orafter the filaments and/or microfibers are formed into a mat or otherpower storage device structure. FIG. 14 shows a bicomponent filamentwith 1120 microfibers per filament, part of which is separated intomicrofibers, formed using the above-described technique of dissolvingout a matrix component.

In various exemplary embodiments, microfibers are formed by spinning 2-4dpf bicomponent yarn filaments, which spinning may be done usingconventional techniques. In various exemplary embodiments, a mildcaustic is applied to the yarn causing individual microfibers toseparate from the bicomponent yarn filament. FIG. 15 shows microfibersmade according to this technique with a dpf of about 0.1.

In some exemplary embodiments, the yarn filaments are separated intomicrofibers without use of a caustic. Splittable, hollow fibers, such asthose illustrated in FIG. 16, may be split without a caustic. In variousexemplary embodiments, a polyester/polypropylene filament is spun andsplit afterward. FIG. 15 shows a filament with 198 3-dpf filaments priorto processing. In various exemplary embodiments, the filaments aremechanically drum to produce 3,168 microfibers with a dpf of about 0.2.

In various exemplary embodiments, and as shown in FIG. 17, microfibersare formed from a bicomponent filament with a first polymer core and asmaller quantity of a second polymer on the tips of a trilobal or deltacross-section filament. In the embodiment shown in FIG. 17, the corepolymer is a melt-spinnable polyurethane and the tips are polypropylene.The ratio of the two polymers is approximately 70% polyurethane to 30%polypropylene. As shown, the filaments are made using standard fullyoriented yarn spin draw processes and has an approximate dpf of 3. Afterspinning, in various exemplary embodiments, the filaments are twistedand subject to wet heat to help produce a filament such as that shown inFIG. 17. The tips separate from the cores forming microfibers with a dpfof about 0.2 or less spiraled around the filament core. The filamentcore may also shrink during the heating process.

In various exemplary embodiments, the microfibers are used “as is”,carbonized, and/or pre-coated with engineered materials (e.g., metals,carbon (e.g., graphite, expanded graphite, activated carbon, carbonblack, carbon nanofibers, and/or CNT), silica, tin oxide, and/or acid).In various exemplary embodiments, the microfibers are pre-treatedutilizing various methods or means. The pre-coated materials may includenano-scale materials such as, for example, nanofibers and nanotubes. Acoating may be applied by deposition via a solvent both in dispersionand slurry form (e.g., by water, acid, or other solvent), by spraying,or by immersing the microfiber (e.g., in a conductive metal). Forexample, many of the materials from which the microfibers may be formedhave a higher melting point than lead-based electrode active materials.Thus, lead-based active material may be applied to the microfibers bydipping the microfibers in molten active material and allowing theactive material to stiffen, solidify, and/or otherwise form on themicrofiber.

The microfibers may be constructed of various materials, includingconductive materials and/or dielectric materials. In variousembodiments, microfibers are made from two or more materials (e.g., aconductive core and a dielectric surface). The microfibers may beconductive in their core or internally and dielectric on their surfaceor externally, which would allow the cores to act as current collectorsfor the capacitors formed by the dielectric material. This may beaccomplished at least in part by, for example, coating a conductivemicrofiber with dielectric.

In various exemplary embodiments, the microfibers are coated with carbon(e.g., graphite, expanded graphite, activated carbon, carbon black,carbon nanofibers, and/or CNT). Carbon materials may be coated orotherwise provided onto the microfiber in their native form (i.e.,without any binder materials) or in a composite form where a knownquantity of binder is added to the carbon to form a stable porouscomposite on the microfiber. CNTs, carbon nanofibers, and carbonwhiskers may also be grown on a variety of microfiber substrates.

In various embodiments, microfiber segments (e.g., short microfiberpieces) are provided on one or more battery grids. In variousembodiments, the microfibers so produced are applied in a “floatingstructure” that may be utilized to help support the active material.

In various exemplary embodiments, a battery electrode is formed usingmicrofibers, wherein the microfibers are carbonized or graphitized andcoated or otherwise provided with active material. In variousembodiments, the microfiber is made from a polymer (e.g., a polyolefin).In various exemplary embodiments, metal particles (e.g., nickel, iron,cobalt, molybdenum) are provided (e.g., applied to its surfaces), whichmay be accomplished by any suitable means such as, for example, byspraying. In various embodiments, the metal particles are substrates orseeds onto which carbon fibers (e.g., CNT) may be formed or grown. Invarious exemplary embodiments, active material is provided or appliedaround the microfibers by, for example, pressing or rolling the activematerial around and/or through the carbon microfiber/nanotubes bundle.In various exemplary embodiments, the bundle is wetted with electrolytesolution. At any point in the process, the individual microfibers may beformed into bundles or mats, which may be woven or non-woven.

Individual microfibers may be straight or non-straight. In variousexemplary embodiments, the microfibers may be coiled, looped, crimped,air entangled, or any combination of these and other shapes.

In various exemplary embodiments, the microfibers are provided orotherwise formed into a mat (e.g., woven, non-woven, or point bonded).In various embodiments, active material (e.g., lead oxide) is provided(e.g., coated) on the microfiber mat to form an electrode for anelectrochemical battery. The microfibers may also be coated with carbonor nanotubes (and, in at least some embodiments, thereby function as anEDLC). Such embodiments may help to increase life cycle, create a highinterfacial area thereby increasing the double layer capacitance for theactive electrode, help optimize charge acceptance and/or high-ratedischarge, and/or improve conversion efficiency of active material(e.g., on initial charge).

In various exemplary embodiments, pieces (e.g., short pieces) ofmicrofibers are interspersed, mixed, or otherwise provided with theactive material. The mixture of short microfiber pieces and activematerial may be provided (e.g., coated) on a conventional chargecollector (e.g., a grid, plate, or screen) or on a fiber mat. In variousexemplary embodiments, short lengths of microfiber may be adhered to thesurface of the charge collector to form a flocking structure to supportthe active material. The inclusion of the short microfiber pieces in theactive material helps increase the electrode's porosity and/orreactivity, which helps reduce the amount of active material required toform an electrode. If the microfiber pieces are coated in carbon, theelectrodes may also be used in an EDLC.

In various exemplary embodiments, a scrim layer, including a microfibermesh, is included in an electrode. A scrim layer may be included betweenthe active material and the charge collector and/or over or embedded atleast partially in the active material. In various embodiments, thescrim layer is formed of microfibers of the types discussed above. Themicrofibers comprising the scrim layer may be pre-coated with materials,such as, for example, active material, carbon, silica, graphite, and/oracid. In various exemplary embodiments, the scrim layer is formed fromand/or coated or impregnated with carbon to help improve capacitance andconductivity (sponge lead and carbon capacitor electrodes). In otherembodiments, the scrim layer is coated or impregnated with carbon andlead oxide to form a dual electrochemical battery electrode and EDLC.The scrim layer may be formed of a woven or non-woven mesh in a varietyof patterns to adjust the ability of the scrim to adhere to and/orsupport the active material. In various exemplary embodiments, a scrimlayer may be utilized as or as part of the collector grid with themicrofibers coupled or connected directly to or otherwise forming orhelping form the plate connector.

According to various exemplary embodiments, a battery cell includes anelectrode with microfibers extending into and/or through the electrode.In various exemplary embodiments, the microfibers help draw theelectrolyte into (e.g., to the electrode's interior) the electrode(e.g., active material) to help improve porosity, increasing theelectrode's effective surface area. In various exemplary embodiments,the microfibers also help maintain the electrode's structural integrityby functioning as pasting or reinforcing fibers (e.g., as the battery ischarged and discharged).

According to various exemplary embodiments, a battery cell includes anarray of microfibers coated with active material (e.g., paste). Invarious embodiments, the microfibers are substantially immersed in theelectrolyte solution. The microfiber arrays may be in any form (e.g.,loose fibers, woven or non-woven mats, bundles, etc.). In variousembodiments, the microfibers act as electrodes (e.g., conduct current),some microfiber arrays coated in anode active material and othermicrofiber arrays coated in cathode active material.

In various embodiments, the microfibers may be made of conducting orconductive polymers which can undergo electrochemical doping (e.g.,P-doping or N-doping), thereby functioning as an electrolytic capacitor.In various embodiments, both types of electrodes may be made of the samematerial capable of undergoing either P-doping or N-doping (e.g., typeIII) to thereby function as an electrolytic capacitor. In variousembodiments, a scrim mat formed at least in part from microfibers madeof conducting polymers may be added to the electrode to provide a EDLCfunctionality to the electrode.

As utilized herein, the terms “approximately”, “about”, “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention, as recited inthe appended claims.

For the purpose of this disclosure, the term “coupled” means the joiningof two members directly or indirectly to one another. Such joining maybe stationary in nature or moveable in nature. Such joining may beachieved with the two members or the two members and any additionalintermediate members being integrally formed as a single unitary bodywith one another or with the two members or the two members and anyadditional intermediate members being attached to one another. Suchjoining may be permanent in nature or may be removable or releasable innature. The term “coupling” includes creating a connection between twocomponents that allows electrical current to flow between thosecomponents.

It is also important to note that the construction and arrangement ofthe electrical power storage devices, as shown in the various exemplaryembodiments, is illustrative only. Although only a few embodiments havebeen described in detail in this disclosure, those skilled in the artwho review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited in the claims.For example, elements shown as integrally formed may be constructed ofmultiple parts or elements, the position of elements may be reversed orotherwise varied, and the nature or number of discrete elements orpositions may be altered or varied. The order or sequence of any processor method steps may be varied or re-sequenced according to alternativeembodiments. Other substitutions, modifications, changes, and omissionsmay be made in the design, operating conditions, and arrangement of thevarious exemplary embodiments without departing from the scope of thepresent inventions, as expressed in the appended claims.

What is claimed is:
 1. A power storage device, comprising: a positiveelectrode having a grid; a negative electrode having a grid; and aseparator separating the positive electrode from the negative electrode;wherein at least the negative electrode or the positive electrodecomprises fibers selected from both a first group consisting of trilobalcross-sectional fibers, quadrilobal cross-sectional fibers, andsubstantially circular cross-sectional fibers, and a second groupconsisting of non-straight fibers having shapes selected from the groupconsisting of a coiled fiber, a looped fiber, and an air entangledfiber; the fibers being provided in an array of wicking fibers loadedwith electrode active material included in the electrode; wherein thewicking fibers constitute either a mixture of fibers selected from afirst group of relatively shorter fiber pieces in addition to a secondgroup of relatively longer fibers, or only selected from the group ofrelatively shorter fiber pieces.
 2. The power storage device of claim 1further comprising microfibers.
 3. The power storage device of claim 1wherein a carbon additive is provided on the fibers.
 4. The powerstorage device of claim 3 wherein the carbon additive comprises at leastone of graphite, expanded graphite, activated carbon, carbon black,carbon nanofibers, or carbon nanotubes.
 5. The power storage device ofclaim 1 wherein the fibers are formed into a mat.
 6. The power storagedevice of claim 1 wherein the fibers are electrical conductors.
 7. Thepower storage device of claim 1 wherein the fibers are electricalinsulators.
 8. The power storage device of claim 1 wherein the fibersare fully coated in electrode active material.
 9. The power storagedevice of claim 1, wherein the fibers form an array of wicking fibersloaded with electrode active material, the fiber array beingsubstantially immersed in electrolyte solution.
 10. The power storagedevice of claim 1, wherein the fibers are formed from a polymer.
 11. Thepower storage device of claim 1, wherein the fibers further comprise acrimped fiber.
 12. A battery comprising at least two grids, activematerial, and a scrim layer, wherein the scrim layer comprises a fibermesh provided between the active material and one or more grids and isembedded at least partly in the active material, and wherein the scrimlayer is comprised of fibers selected from a group consisting of acoiled fiber, a looped fiber, and an air entangled fiber.
 13. Thebattery of claim 12, wherein the scrim layer is further comprised offibers selected from a group consisting of trilobal cross-sectionalfibers, quadrilobal cross-sectional fibers, and substantially circularcross-sectional fibers.
 14. The battery of claim 12, further comprisinga separator, wherein the scrim layer is provided between the separatorand a grid.
 15. The battery of claim 12 wherein the scrim layer is atleast partially coated with short fibers in a flocking structure. 16.The battery of claim 12 wherein the scrim layer is a woven or non-wovenmesh.
 17. The battery of claim 12 wherein the scrim layer is a fibermat.
 18. The battery of claim 17 wherein the fiber mat comprises fibersmade of glass.
 19. The battery of claim 12 wherein the fiber mesh iscomprised of a polymer.
 20. The electrode of claim 19, wherein thepolymer is selected from the group of polyester, polypropylene,polyethylene, and polyethylene terephthalate.
 21. The battery of claim14, further comprising a second scrim layer provided on the second gridso that the two scrim layers surround the separator.
 22. The battery ofclaim 12, wherein the scrim layer is formed of a woven or non-woven meshin a pattern to adjust to the ability of the scrim to adhere and/orsupport the active material.
 23. A power storage device, comprising: atleast one positive electrode; at least one negative electrode; and a matcomprised of a plurality of fibers, wherein the fibers are selected fromboth of two groups, the first group selected from the group consistingof trilobal cross-sectional fibers, substantially circularcross-sectional fibers, and quadrilobal cross-sectional fibers; and thesecond group selected from the group consisting of a coiled fiber, alooped fiber, an air entangled fiber and combinations of the foregoing,and wherein the mat is woven.
 24. The power storage device of claim 23wherein the mat further comprises microfibers.
 25. The power storagedevice of claim 23 wherein an additive is provided on the fibers.
 26. Apower storage device, comprising: at least one positive electrode; atleast one negative electrode; and a mat comprised of a plurality offibers, wherein the fibers are selected from both of two groups, thefirst group selected from the group consisting of trilobalcross-sectional fibers, substantially circular cross-sectional fibers,and quadrilobal cross-sectional fibers; and the second group selectedfrom the group consisting of a coiled fiber, a looped fiber, an airentangled fiber and combinations of the foregoing, and wherein thefibers further comprise a crimped fiber.
 27. The power storage device ofclaim 26 wherein the mat further comprises microfibers.
 28. The powerstorage device of claim 26 wherein an additive is provided on thefibers.